This invention is in the field of spray booths utilized for electrostatic powder coating of products. It is the practice to convey the products to be coated through an electrostatic spray booth wherein the powder is sprayed onto the products which are then subsequently moved out of the spray booth and into a heating chamber.
The spray powder which does not cling to the product is subsequently collected and reused. Frequently, the color of the spray powder is changed depending upon the color requirements of the end product. It is therefore necessary to ensure that the salvaged spray powder of one color is not mixed with the salvaged spray powder of another color. One attempt to limit such mixing is by placing removable plastic sheets against the interior walls of the chamber within the spray booth. The plastic sheets are removed prior to the change in the color of the spray powder. Another approach such as disclosed in United Kingdom patent No. 1,588,503, issued to Toff, is to emit jets of pressurized air perpendicularly from the metal side walls of the spray booth chamber to prevent the electrostatically charged powder from clinging to the metal interior walls of the chamber. I have determined that superior results are provided when the air is not turbulent within the chamber, but instead emitted to flow parallel to the inner walls of the chamber thereby creating an air curtain or wall adjacent each of the interior walls of the chamber. In the booth disclosed herein, the spray powder which does not cling to the product rides on the air wall adjacent each interior wall to an exit conduit wherein the powder is withdrawn and collected.
In the Swiss patent No. 560,558, an electrostatic spray booth is disclosed wherein pressurized gas is utilized to collect the unused spray powder with an exit opening provided at the bottom of the chamber. In the booth disclosed herein, the pressurized gas emitted into the chamber is directed by a plurality of louvers oriented to direct all of the pressurized gas to the exit conduit. As such, the unused powder is prevented from collecting in any particular location within the chamber such as upon the bottom wall. Further, the louvers disclosed herein project exteriorally of the spray booth chamber minimizing turbulence within the chamber. Such orientation and positioning of such louvers have heretofore not been known.